The present invention relates to a method for painting pretreatment of a plastic formings and a cleaner for painting pretreatment.
Since a plastic bumper for an automobile makes some contribution in production of a light weight of automobiles and is superior in moldability, the plastic bumper is a main current in the automobile bumpers. In particular, since a bumper made of a polyolefin resin bumper has an advantage in the moldability and economical cost, it has been widely adopted. However, since the polyolefin resin formings is chemically inactive, the adhesion of a paint film is not satisfactory.
Thus, there have been made various kinds of proposals from the sides of material, coating, and painting pretreatment, and some of the proposals are practically used.
In the side of material, there have been reported a material in which a resin of good adhesive strength is blended with a polypropylene resin (refer to Japanese Official Patent Provisional Publication, showa 48-43441) and a material in which a polystyrene resin and an elastomer are used in combination (refer to Japanese Official Patent Provisional Publication, showa 52-141854) and so on.
In the side of coating, there has been proposed a primer composition for painting, which contains a dissolved chlorinated polyolefin, a material made of a polypropylene resin (refer to Japanese Official Patent Provisional Publications, showa 58-8734 and showa 58-15535).
In the side of painting pretreatment, there has been proposed a method in which an inactive polyolefin resin formings is treated with plasma and a functional group is introduced into a surface of the formings in order to elevate the adhesion of a painting film (refer to Japanese Official Patent Gazette, showa 60-46133).
However, in the formings which is obtained from a variously-improved polyolefin resin by an injection molding or an extrusion molding etc., a mold release agent is tightly attached on the formings surface or also, so-called WBL (Week Boundary Layer) is often formed by that a non-crystalline polyolefin resin or a resin having low molecular weight undergo a surface-concentrating. Such dirt as a mold release agent and WBL etc. disturbs the adhesion of a painting film. Therefore, unless the dirt is taken out, an adhesion-elevating effect on a painting film resulting from said plasma treatment and primer composition can not sufficiently be expected.
Hitherto, such dirt as the WBL is removed by a vapor-washing method using a chlorinated hydrocarbon such as 1,1,1-trichloroethane (hereinafter, referred to as "TCE"). The vapor-washing method by TCE is superior in a washing effect and mass production, and is widely adopted.
However, since the chlorinated hydrocarbons, for example TCE, has a problem of air-pollutio, water-pollution, and, especially, destruction of the ozone layer of earth, they are all discontiued in a whole world in a year of 2005 and are no longer used (a Montreal protocol of the second meeting of the Contracting States, Jun. 26th, 1990).
Therefore, it is required to undergo painting pretreatment of a plastic formings by a method which does not cause said environmental destruction. As a method of this kind have been considered, instead of the chlorinated hydrocarbon, to adopt a solvent in a hydrocarbon series which have a washing effect in an extent similar to that of the chlorinated hydrocarbon. However, there is such a problem as the solvent in a hydrocarbon series easily ignites and requires carefulness in handling when it is used for the vapor-washing method.
Therefore, the subject of the present invention is to provide a method for painting pretreatment of a plastic formings which is replacable of a hitherto-known vapor-washing method wherein the chlorinated hydrocarbon being used, is effective on the painting pretreatment of a plastic formings, and does not cause the environmental destruction, and in addition, to provide a rinsing agent for degreasing which is used for the forementioned method.